In the application of cementitious materials to closed cell generally smooth skinned foam materials such as styrene polymer foams, difficulty is experienced in obtaining an adequate and permanent bond between the contacting surfaces of the dissimilar materials. This is due at least in part to the fact that the prior known cementitious materials in setting, tend to shrink whereas the foam surface with which it comes in contact does not undergo a corresponding shrinkage. Also, the differences between the coefficients of thermal expansion between the two types of materials often provides a severe shearing stress which results in failure of the bond between the materials.